Silicon Nitride Waveguide Technology: TriPleX®

Silicon nitride(SiN) TriPleX® is our proprietary waveguide technology for photonic integrated circuits (PICs). LioniX International has been pioneering the use of silicon nitride in integrated photonics since 2001 and has an extensive library of building blocks for both photonic integrated circuit design and module development.

TriPleX® waveguides have the lowest propagation losses reported in SiN (0.1 dB/cm down to 0.1 dB/m). Silicon nitride waveguides are suitable for a wide range of photonic integrated circuit applications, operating in a broad wavelength band from 405 nm to 2350 nm.

Silicon nitride waveguide TriPleX® journal article:

Low-Loss Si3N4 TriPleX Optical Waveguides: Technology and Applications Overview

TriPleX®  whitepaper

Get an in-depth look at the strengths and applications of the TriPleX® waveguide platform.

Front cover of the silicon nitride triplex whitepaper

Different waveguide cross-sections showing silicon nitride waveguide in silicon oxide substrate.

TriPleX® waveguide structure

TriPleX® waveguides come in different cross sections (left). The cross sections range between box shapes, single stripe, and double stripes. The latter coming in two forms; the symmetric double stripe and the asymmetric double stripe (ADS). Finally the TriPleX® family has a buried waveguide for very thick nitride layers.

Double stripe silicon nitride

Each of these cross sections have different properties optimized for use in a specific application: The asymmetric double stripe cross section is our workhorse at 1550 nm applications and is offered as well via our multi project wafer (MPW) services. The losses of this waveguide are < 0.1 dB/cm and with the taper the fiber coupling losses are below 0.5 dB per facet.

Ultra low-loss waveguides

The single stripe version of TriPleX® is used for ultra low loss applications (losses as low as 0.1 dB/meter) or in applications in the visible light domain. In the visible domain the single stripe is optimized for fiber coupling as well low loss propagation of the wavelengths between 405 to 700nm.

Waveguides engineered for integration

As a low loss passive waveguide material, silicon nitride has no native light generating capability. LioniX International solve this by engineering TriPleX® waveguides for excellent input and output coupling (to fibers, gratings, mirrors and other PICs), enabling integration with a wide range of optimized components for light generation, modulation and detection. We call this approach to photonic module design “hybrid integration” and it underpins higher levels of functionality in a great range of photonic integrated circuit applications including:

In order to enable this high level of integration, LioniX International has developed a patented tapering method to convert low contrast modes for optimal fiber coupling, to high contrast modes for small bending radii. This novel building block, known as a spot size converter, further extends the applicability of TriPleX® waveguides to devices that require high levels of integration and highly optimized performance.

hybrid integrated dual gain laser

A hybrid integrated dual gain laser with indium phosphide gain sections (gold) and a silicon nitride tunable external cavity (grey).

Tunable and reconfigurable photonic integrated circuits

The careful control of light confinement in TriPleX® waveguides enables the integration of on-chip actuators for solid-state tuning, actuation or modulation in PICs. This is a powerful capability when combined with the optical properties of the silicon nitride platform. LioniX International currently offer two types of on-chip actuators on a commercial basis:

  • Thermo-optic actuation
  • Stress-optic actuation

Our platinum thermo-optic actuators utilize the resistivity of the metal to heat up the waveguide and change its refractive index, causing a change in phase. Thermo-optic actuators are widely used in photonics, and ours provide industry-standard performance in terms of speed and power consumption.

The stress-optic actuator represents a novel improvement in phase modulation. The design employs lead zirconate titanate (PZT), which is a particularly efficient piezoelectric material commonly used in MEMS applications. The use of mechanical stress, as opposed to heat, ensures less cross-talk between adjacent actuators. Moreover, we maintained the minimal optical losses of our TriPleX® waveguides by keeping the active components of the actuator away from the light path. The result is an actuator that is stable over time, repeated use, and in different environmental conditions. It switches 50-times faster than a thermo-optic actuator and consumes 100,000-times less power in quasi-DC operation.

This is the optical phase modulator for environmentally friendly and economic power budgets, especially in applications like microwave beamforming, LiDAR, and communication systems.

MPW: Easy access for silicon nitride photonic waveguide technology

Multi Project Wafer (MPW) runs provide cost-effective easy access to TriPleX® waveguides. Design photonic integrated circuits using freely available process design kits (PDKs) and qualified standard building blocks.